Microwave sparking?

Sparks or blue flashes inside the microwave are arcing, and it is usually something in the cavity: metal, a burnt-on splatter, or a damaged panel on the inside wall. Stop it and unplug it the moment it sparks, then look for the cause before you run it again.

Not sure which one it is? Snap your microwave and we’ll narrow it down.

Does it run but not heat the food?

A microwave that doesn't heat has different causes. Microwave not heating

Likely causes

  1. Metal in the cavity

    Most commonEasy DIY

    Sparks start with a plate or container in the microwave. Look for foil, twist ties, a metal-rimmed or gold-trimmed dish, a travel mug or a takeout container with a metal handle.

  2. Food splatter carbonized on the walls

    Most commonEasy DIY

    Dark, crusty or greasy spots on the inside walls, ceiling or floor, and sparks that appear near them even with a plain bowl of food.

  3. Damaged or dirty waveguide cover

    CommonModerate DIY

    A small panel on the inside wall (usually the right side) is scorched, cracked, greasy or has a hole burned in it, and the sparks come from that spot.

  4. Peeling interior paint

    CommonCall a pro

    Flaking, bubbling or bare metal on the cavity walls where the paint has worn away, with sparks near those patches.

  5. Bent rack support

    Less commonEasy DIY

    On models with a metal rack, a rack that touches the wall or a support that is bent or loose, and sparks where the rack meets the wall.

  6. Failing diode or magnetron

    Less commonCall a pro

    Sparking or loud buzzing with an empty, clean cavity and no metal or damage inside, often with weak or no heating. These parts are behind the outer case.

    Part: $55–200 for a pro repair (diode $55–130, magnetron $100–200)

Quick checks

Stop the microwave and unplug it the moment it sparks, and never run it empty. If there is smoke or a flame inside, keep the door shut and unplug it. If the fire doesn't go out within a few seconds, leave and call 911. Never open the outer cabinet: the high-voltage capacitor inside can hold a dangerous charge even when unplugged, so anything behind the outer case (fuse, diode, magnetron, capacitor) is for a pro. Don't use it if the door is damaged or won't close properly. Over-the-range units are heavy and need two people to remove.

  1. Stop it and unplug it the moment it sparks. Never run it empty to test it.
  2. Check what was inside: foil, twist ties, metallic trim on dishes, a metal-handled container or a travel mug.
  3. When it is cool, look at the inside walls for burnt-on splatter, and wipe them with a damp cloth and mild soap.
  4. Look at the waveguide cover, the small panel on the inside wall, for scorch marks, cracks or a hole.
  5. Look for peeling or bare patches of paint, and on models with a rack, check that it sits on its supports and isn't touching the wall.
  6. Write down the model number from the label, and take photos of any scorch marks.
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Snap one of these:

  • the inside walls and the waveguide cover (the small panel on the side wall)
  • any scorch marks or peeling paint inside
  • the model label (inside the door frame or on the back)

Add a note or more photos next. Nobody calls you.

When to call a pro

The cavity is clean and empty and it still sparks, the waveguide cover or interior paint is burned through, the door is damaged, or there was smoke or a flame. A budget countertop microwave over 10 years old is often cheaper to replace than repair. For lifespan and upkeep, see the microwave guide. If it runs but doesn't heat, see microwave not heating.

Typical cost: $100–200 for a typical microwave repair (about $175), up to about $500 for door replacements and built-in or over-the-range units. Expect a $50–100 service call plus $50–150 an hour in labor. Countertop repairs run $50–350 and over-the-range or built-in repairs $50–500.

Sources: HomeAdvisor: How much do microwave repairs cost? (updated June 19, 2026)

After a scan, Fixology can also help you find pros near you.

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Fixology helps you understand your home — it isn't a substitute for a licensed pro on serious gas, electrical, or structural work.